This invention relates to a barge-carrying water-borne vessel with at least two tiers of barge holds and a lock for flotation loading of barges into those holds. More particularly, the invention relates to a means for employing the otherwise unoccupied space of the lock for stowing a plurality of barges during a voyage. The invention also relates to a bow-loaded multi-tiered vessel using locks for flotation loading.
Many problems, often related to the high cost of labor, have recently changed the economic and technical natures of shipping. For example, for many centuries materials have been transported by barges on rivers, lakes, canals, and inland waterway systems to ports near the river mouth, unloaded there from the barges, loaded onto ocean-going vessels, sent to other ports across the sea, unloaded there, and reloaded in many instances onto other barges to be shipped up another river system. In recent years, however, the costs of loading and unloading cargo have risen higher at an ever-increasing rate. Containerizing of cargoes has helped somewhat, but even then, as well as in bulk-loaded barges, there has remained the necessity of unloading the barges at one port, placing the container and other cargo on a pier, and then loading from the pier into an ocean-going vessel, only to require the reverse procedure in the ports to which the cargo is carried by that vessel. All this adds considerably to the ultimate cost of the product concerned, and the time required for transportation.
An apparent answer to the problem is to ship the barges themselves. Since they cannot undergo an ocean voyage directly in the water, this would require loading the barges aboard an ocean-going vessel. However, few vessels are capable of carrying a series of barges aboard, and the problem of loading barges on the vessels must be confronted. The barges are often very large and heavy; cranes or elevators to lift them would be very expensive. In fact, large river barges cannot be lifted by cranes or elevators.
Recent inventions such as our U.S. Pat. No. 3,913,512, issued Oct. 21, 1975, and our co-pending application, Ser. No. 105,414, now abandoned, filed Dec. 19, 1979 have proposed flotation loading of barges and other cargo-carrying containers into barge-carrying ships. Since the barges are already in the water, flotation loading can be employed with a specially constructed ship that has a suitable hold and a gate through which the barge may be floated into the hold.
However, barges are not as easily handled as are smaller cargo-carrying containers; so particular provisions have had to be made for them. Many barge types are long relative to their beam. The barges used on the Mississippi and Rhine rivers, for example, are very long compared to their width; the Mississippi barges are more than 60 meters long and more than 10 meters wide. For a barge-carrying system to be practical, the ocean-going, barge-transporting vessel must be able to carry many barges. A ship able to accommodate only a single line of barges would, of necessity be extraordinarily long and narrow to be profitable. This general problem was solved in our U.S. Pat. Nos. 3,978,806, issued Sept. 7, 1976; and 4,135,468, issued Jan. 23, 1979. Those patents relate to a vessel having a plurality of longitudinal holds, side by side, either two or three parallel holds, each of which can take the full width of a barge and each of which can accommodate several barges in line or tandem. Also, the problem of loading and unloading the vessel with barges was alleviated by mechanisms shown, for example, in our U.S. Pat. No. 4,147,123, which issued Apr. 3, 1979.
A problem that arises as soon as one attempts to load two or more tiers of barges in a single vessel, is the problem of draft. A few ports can accommodate drafts up to 75 or 80 feet, drafts that exceed those of most vessels, so that their depths would accommodate a ship loading two or more tiers of barges. However, most ports have depths less than 40 feet. A system restricted to voyages between deep-draft ports would not be econimically practical. For this reason, the preferred form of these barge-carrying vessels has a lock disposed at one end, for hydraulically elevating barges to the various tier levels in floatation loading. This broadens the range of barges on which the system can operate; not requiring any special roller mechanisms for dry loading and unloading. It also increases the number of ports which may be serviced.
The economic feasibility of this mode of transportation depends on being able to load and carry the maximum amount of cargo in a minimum of space. Each unused or unusable area in the vessel detracts from its profitability. It is, therefore, desirable to maximize a vessel's efficiency by using as much potential cargo-carrying space as possible.
To that end, a problem has arisen. The space occupied by the loading lock has been generally unusable for the transportation of cargo. At best, it had been possible to store and transport one barge on the bottom of a lock. Since the lock typically extends from the lowest tier to the upper deck of such vessels, space which could otherwise be used to store at least one extra barge for each tier of longitudinal barge holds serviced by the lock has remained unused. This was primarily because of an inability to securely support barges at multiple levels of a loading lock without interfering with the operation of the lock when loading.
One recently proposed system as illustrated in our co-pending application Ser. No. 105,414, now abandoned employs horizontal barge support members which can be projected our from and retracted into the side bulkheads of a loading lock. This solution, however, gives rise to other problems of inefficient space use because storage space on the sides of the lock's bulkheads is required to receive these sliding supports when they are not in use. This reduces the otherwise usable storage space and severely limits the number of adjacent, independently operating locks which may be disposed together at the end of a vessel.
Heretofore, no one has proposed a feasible system of this kind. For example, the vessel shown in the Vargas U.S. Pat. No. 3,939,790, which issued Feb. 24, 1976, involves flotation loading and unloading and accommodates up to three tiers of relatively small lighters, especially designed to be lifted or hung by their ends, but the vessel cannot support full size river barges. Vargas shows a hold having supporting brackets which are movable out of the side walls of the dock chamber. The Vargas supports are stored flush against the side walls or bulkheads in a recess, and swing out along a vertical axis to provide points of support to the side edges of barges. The supports are received by sockets in the lash type barges which the system is designed for, and requires careful placement of the barge. These supports, however, are designed for loads which are far lighter than the barges transported in the vessel of the present invention. Furthermore, since only points of support are provided, and not an extended surface on which to support the barges, a great deal of instability is inherent in the use of the system.
Thus, an important object of the invention is to provide a means and a method for supporting a barge at each level within a loading lock.
Another object is to provide barge support means entirely disposed at all times within the lock, and yet not interfering with the loading operation.
Another object of the invention is to provide a broad support surface for supporting a barge at various upper levels in the lock of a barge-carrying vessel, the apparatus providing the support surface being readily stored in the side bulkheads of the lock, yet easily and automatically erected, and not interfering with lock operation.
Yet another object of the present invention is to provide an efficient and simple system for maximizing the usuable barge transporting area of a flotation-loading waterborne vessel to include the upper areas of the loading locks.